Who among us hasn't wondered how our children, who we're raising almost identically to one another, could be turning out so dramatically different? How, in fact, did we turn out to be so different from our own brothers or sisters?It's in the genes, say some, the "nature" part of the nature/nurture equation.

It's essentially what people mean when they say about their kids, "They just came out of the womb that way.

However, few of us stop there, because few people think personality is primarily predetermined at birth. But how much of our children's – or even our own – personalities are influenced by birth order?

That question has been around so long you'd think the experts would have an answer by now. In fact, they have lots of answers – along with opinions that range from being subtly different to polar opposites.

Typical Traits

The idea that being the eldest, middle or youngest child comes with some typical personality traits has been around since the 1920s, when Austrian psychologist Alfred Adler began stressing the importance of birth order on personality and character.

Adler believed that humans have a strong need to be accepted and valued, and that family is the first social group in which we strive for this sense of belonging.

His theory, and the views of several birth order experts since, boils down to this: Children in any given family each strive for their parents' love, attention and resources. The bigger the family, the harder it is to do this. And depending on where a child falls in the family, he or she responds differently.

The Eldest Child

Firstborn children don't have to work very hard for their parents' attention and resources. Adler proponent Jack Agati, a birth-order expert, family counselor and public speaker, offers the example of the well-organized photo albums documenting every stretch, splash or stroll in the early life of many firstborns. Firstborns learn that all it takes to gain parent approval is to follow Mom's or Dad's wishes, according to Adler's theory. And some say eldest children maintain this approach throughout their lives, gaining status by working hard, not making waves – in a nutshell, the good kid who wants to do the right thing, sometimes to the point of perfectionism.

But first children also experience being "de-throned" when younger siblings come along. Some see this as the defining factor in an eldest child's life – losing that status and doing what it takes to get it back, by aligning with parents or other authorities. That may be why firstborns also tend to be emotionally intense and driven, according to birth-order theorists.

Middle Children

It's commonly observed that parental focus lessens with latter-born children. (What photo album?) As a result, the second-born and any other "middles" need to be more intuitive, more creative in capturing a parent's attention, notes Agati. They are more tuned-in types, according to Adler's theory. They amass data on what will draw and maintain a busy parent's attention and they quickly learn that adaptability is an advantage, Agati says.

The Youngest Child

The youngest child may either face the same struggle for attention and resources as his older "middle" siblings, or – particularly if there's a large gap in age – he may enjoy similar status as a firstborn since his parents have more time to focus on him.

Youngest children tend to be comical and entertaining, very social, and babied by both their parents and older siblings, Agati explains. Having raised several children already, parents may have lower expectations for their youngest, which in turn can mean that the youngest child has lower expectations for himself.

Dueling Dogmas

Psychologists and sociologists have conducted hundreds of studies on birth order throughout the world over the past century. The personality traits described in Adler's "social truth" birth order theory have held true for many, but some modern-day experts see things a little differently. Psychologist Frank Sulloway's 1997 tome Born to Rebel has gained considerable attention. Currently a visiting scholar at the Institute for Personality and Social Research at the University of California – Berkeley, Sulloway takes an evolutionary, or Darwinian, view of the effects of birth order.

While Adler focuses on the human need to feel valued – to belong – Sulloway points to siblings' competition for a host of parental offerings. "Siblings are competing for all the goodies," he observes, listing these as "parental investment, love, affection and other family resources." Depending on their birth order, Sulloway says kids fairly consistently position themselves to "maximize access to those resources." His theory assumes different motivations than Adler's, but the birth-order effects he reports are similar. The firstborn "gets brownie points for being helpful and responsible," Sulloway says, adding that firstborns are "over-represented at Harvard, Princeton and Yale."

"The easiest niche [to acquire] is the first – the surrogate parent role," Sulloway says.

"Openness to experience is the engine by which [younger] siblings find their niche. They need to diversify." Sulloway, who reviewed mountains of research before concluding that there is clear evidence of birth-order effects, says latter-borns are more likely to be unconventional, indeed "more likely to start a revolution." Sociologist Dalton Conley, author of the just-published book The Pecking Order, takes a much different tack. The director of New York University's Center for Advanced Social Science Research and a research associate at the National Bureau of Economic Research, Conley believes the evidence of psychological differences due to birth order is rather weak.

"People confuse birth order and family size," he says, reporting that what may look like birth-order effects are really the results of economic realities. As Conley sees it, the success rate of firstborn children has to do with the resources of money and attention that parents can typically offer a firstborn. As more kids enter the picture, those resources have to be divided. "Firsts and lasts each get some time as an ‘only,'" Conley says, noting that this is economically most advantageous. "Middles get short shrift," he adds. "They're always fighting a two-front war."

And then there's Judith Rich Harris, author of the Pulitzer Prize-nominated book The Nurture Assumption: Why Children Turn Out the Way They Do. Dismissing much of the previously mentioned theories, she argues that birth order cannot account for personality differences among siblings, because peers outside the family are the biggest influence on children's personalities – not family relationships.

Citing numerous studies, Harris makes a thought-provoking claim: Kids don't act the same or play the same roles outside of their families as they do within their families.

The View From the Front Lines

So what do you do with all of this birth-order research and theory? Parents generally don't consider birth order as the sole definer of their children's personalities. Some find that it applies to their kids; others do not. "I think about birth order all the time," says Lori Silverstone, a mother of three. "My kids all have very distinct personalities. You wonder why that is. They all came from the same family, yet they're really different."

She describes her oldest, Talia, as "more impulsive and high-strung." "She's the oldest; we were more nervous as parents. We responded to her more quickly and she's come to expect a lot of that," Silverstone says. Her second-born, Ilana, "tends not to be so demanding. She's able to wait, able to deal with disappointments," Silverstone says. "She's very resourceful, very even, very together.

We were more relaxed parents with her." Of her youngest, Ben, 4, Silverstone says, "he is used to being babied a lot. The girls hover over him. … His two older sisters talk a lot for him. He has to be more of a fighter, fighting for his own voice."

But while her kids fit many of the traditional birth-order characteristics, Silverstone wonders if her children aren't simply wired this way, regardless of where they fall in the family. Linda Snyder, a mother of a 13-year-old daughter and an 18-year-old son, sees few of the classic oldest-child characteristics in her son. But she wonders whether the gap of five or more years between her kids is the reason why.

As the youngest child in her own family, Snyder remembers that the oldest was expected to follow a career path chosen by their parents. "As youngest, I had more leeway," she recalls. Now with her oldest child headed into the military and her youngest aspiring to a career in drama or dance, Snyder wonders whether her children's different choices were influenced by gender, talent or birth order. Certainly there are other factors that influence a child's character: health issues, family crises, parents' personalities and more.

Even birth-order theorists note that personality characteristics and future success are not predestined. Not all eldest children are cautious conservatives. Lots of latter-borns are driven and highly accomplished. Yet, some valuable parenting lessons emerge when you look at birth order and children's personality traits.

Giving Each Child His Due

Judy Freedman Fask provides a counterexample to birth-order stereotypes. Since she is the seventh of eight kids, some birth-order theories would pit her as the least successful or the most lost in her large family. She was the last of a long series of middle kids and never had the opportunity, even temporarily, to be an only child. But Freedman Fask is now a mother of five with a highly successful career as director of a collegiate deaf studies program.

She's also an active volunteer in her community. It's her oldest sister who has taken the "alternative route," moving furthest away from her parents, teaching aerobics, working as a waitress "and living a life filled with freedom," Freedman Fask says. In fact, the family Freedman Fask grew up in meets few of the stereotypes of large families, including the pitfalls of limited resources.

She credits her dad, who was able to manage the resources of his attention despite a tribe that spanned 13 years. "At dinnertime, my father would go around the table and ask each of us individually how our day was," she recalls. "And each of us would sit quietly and listen until everyone was done." Socioeconomic theorist Dalton Conley believes that most of the time parents aren't aware of family inequities.

"If they were, they would correct for it." The way to manage the resource issue, he advises, is to plan ahead, especially when it comes to finances. Jan Rybeck, a mother of three, talks about her family's division-of-assets dilemma as if she herself has just finished chatting with Conley. "We decided to pay for private education for each of the kids for a few years," she says. "When we couldn't afford it for all of them, we decided they'd all go to public schools." Freedman Fask's advice, based on the model her parents provided, is to "be fair and equal with the love you show your kids... But also respond to kids' differences."She takes turns doing something special with her kids one at a time, an approach recommended by the professional experts as well. Conley notes that this becomes especially important for middle kids who can get lost in the shuffle. "Parents tend to emphasize ‘family time' with everyone together," he says. "Make sure you get to spend alone time with your kids so they get individual parent attention too."

"It's important to value each offspring on different scales," counsels Sulloway. "If the first is good at school, it's not good to compare the second to the first on his studies. Parents need to reinforce the things kids are good at that are different."

When Your Birth Order Comes Into Play

Parents' own birth order can become an issue when dynamics in the family they are raising replicate the family in which they were raised. Agati notes common examples, such as a firstborn parent getting into "raging battles" with a firstborn child. "Both are used to getting the last word. Each has to be right. But the parent has to be the grown-up and step out of that battle," he advises. When youngest children become parents, Agati cautions that because they "may not have had high expectations placed on them, they in turn may not see their kids for their abilities."

But he also notes that since youngest children tend to be more social, "youngest parents can be helpful to their firstborn, who may have a harder time with social situations. These parents can help their eldest kids loosen up and not be so hard on themselves. Mom Susan Ritz says her own birth order didn't seem to affect her parenting until the youngest of her three children, Julie, was born. Julie was nine years younger than Ritz's oldest, Joshua, mirroring the age difference between Susan and her own older brother. "I would see Joshua do to Julie what my brother did to me," she says of the taunting and teasing by a much older sibling.

"I had to try not to always take Julie's side." Biases can surface no matter what your own birth position was, as Lori Silverstone points out. "As a middle myself, I can be harder on my older daughter. I recall my older sister hitting me," she says of her reactions to her daughters' tussles.

"My husband is a firstborn. He's always sticking up for the oldest. He feels bad for her that the others came so fast. He helps me to see what that feels like, to have that attention and then lose it." Silverstone sees birth-order triggers as "an opportunity to heal parts of ourselves. I've learned to teach my middle daughter to stand up for herself. My mother didn't teach me that. I'm conscious of giving my middle daughter tools so she has a nice way to protect herself."

Whether or not you subscribe to theories that birth order can affect your child's personality, ultimately, "we all have free will," Agati notes. It's important for both parents and kids to realize that, despite the characteristics often associated with birth order, "you're not locked into any role."

Understanding Human Nature, by Alfred Adler, translated by Colin Brett, Hazelden Foundation, 1998. The most recent edition of Adler's book espousing social-truth theory and how the basic human need to be accepted translates in birth order.